Within the scope of the invention, wood panels particularly means fiberboard such as MDF or HDF or also LDF, for example. Basically, however, plywood and consequently applying glue to chips and similar particles are also covered. Glue application means spraying the fibers with a glue or binder such as, for example, isocyanate, melamine resin formaldehyde (resins), urea formaldehyde (resins), urea formaldehyde (resins), melamine resins, phenolic resins or other resins, for example on the basis of polyamines or tannins. During production of wood-product panels, e.g. fiberboard, a mat of bulk material is formed from the glued fibers, the mat is then compressed in a press with application of pressure and heat to produce a wood-product panel or a wood-product panel web. The press can be a cycled press or a continuously operating press. Applying glue to the fibers has particular importance within the scope of the production of such wood-product panels. This is because the properties of the wood-product panels produced, e.g. their transverse tensile strength, are decisively dependent on the amount of glue used. In order to produce wood-product panels having sufficient transverse tensile strength, significant glue consumption is therefore generally required.
Within the scope of the invention, glue application takes place in a blow-conduit, also called a blow-line. In this technique, the fibers are generally produced from comminuted chips, in a defibrator (refiner), and the fibers are blown out of the refiner into the blow-line. A relatively high steam pressure is present in the refiner. This steam simultaneously forms a transport means that conveys the fibers along the blow line. By the blow-line, the fibers reach a downstream dryer. During blow-glue application, spraying of the fibers with glue takes place in the blow-line, and consequently (directly) downstream of the refiner.
An apparatus for blow-glue application is known, for example, from DE 10 2008 059 877 or DE 10 2009 006 704.
It is basically known that injection of the glue into the blow-line by nozzles has a significant influence on the glue-application quality. Therefore, in practice, one basically strives to achieve the finest possible atomization of the glue in order to form relatively small glue droplets. In this way, clumping of the fibers is supposed to be prevented, and, in particular, a glue is used sparingly. For this reason, it has already been proposed not to atomize the glue by simple compressed air, but rather by using steam. For this purpose, two-substance nozzles are used. Such two-substance nozzles are known, for example, from DE 20 2010 005 280.
Blow-line glue application has basically proven itself. However, it is capable of further development. This is a method that has been well tested for a long time, but the amount of glue used continues to be relatively high. This is where the invention takes its start.